Potassium channels which are one of the mechanisms that control systemic physiological actions are distributed in systemic cellular systems including pancreatic .beta.-cells and cardiac muscle and, therefore, drugs that have pharmacological actions to control potassium channels are currently used in the treatment of various circulatory diseases as, for example, antidiabetic drugs, antiarrhythmic drugs, etc. A number of compounds are known in the prior art as such potassium channel blockers. For example, glybenclamide which is an oral antidiabetic drug that blocks potassium channels in pancreatic .beta.-cells has been reported to block ATP-dependent potassium channels in pancreatic .beta.-cells and thereby induce insulin release, hence exhibiting a hypoglycemic action; this action is considered to be a mechanism of action common to oral antidiabetic drugs having the basic structure of sulfonylureas as the skeleton. In this connection, 4-substituted benzoic acid derivatives are known to have the same action as reported in two reference, European Journal of Pharmacology, 141, 243-251 (1987) and British Journal of Pharmacology, 93, 61-68 (1988). On the other hand, compounds that block potassium channels in the cardiac muscle have an antiarrhythmic action and, according to Vaughan Williams, they are classified as antiarrhythmic drugs of class III (see Anti-Arrhythmic Action, E. M. Vaughan Williams, Academic Press, 1980). Examples of such compounds have recently been put forward in Japanese Patent Publication No. Hei 3-60814 and European Patent Publication No. 0245997 as antiarrhythmic drugs that are compounds represented by the following general formula (A): ##STR3## R.sup.a is --NO.sub.2, --NH.sub.2 or --NHSO.sub.2 R.sup.1, where R.sup.1 is a C.sub.1 -C.sub.4 alkyl group;
However, the so far proposed prior art potassium channel blocking antiarrhythmic drugs including the above-described compounds are not necessarily satisfactory in their action and even those which have a certain degree of activity have problems such as the manifestation of serious side effects and it is strongly desired today to develop potent and safe antiarrhythmic drugs that have an outstanding potassium channel blocking action and which yet are substantially free from side effects and hence can safely be used.
Under these circumstances, the present inventors studied a wide variety of compound species for their potassium channel blocking action and their utility as antiarrhythmic drugs and confirmed, as a result, that specified novel amines of the general formula (I) defined above and salts thereof were less in side effects while exhibiting a potent potassium channel blocking action. The present invention has been accomplished on the basis of this finding.